Modulator sequences mediate oxygen regulation of CYC1 and a neighboring gene in yeast [Saccharomyces cerevisiae]

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 80; no. 1; pp. 151 - 155
• Main Authors: Lowry, Charles V., Weiss, Joan L., Walthall, Deborah A., Zitomer, Richard S.
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences of the United States of America 1983; National Acad Sciences
• Subjects: Cell growth; Cytochrome c Group - analogs & derivatives; Cytochrome c Group - genetics; Cytochromes c; DNA; Gene Expression Regulation; Genes; Genetic mutation; Messenger RNA; Operon; Oxygen; Oxygen - physiology; Plasmids; Repression; RNA; RNA, Messenger - genetics; Saccharomyces cerevisiae; Saccharomyces cerevisiae - genetics; Saccharomyces cerevisiae Proteins; Transcription, Genetic; Yeasts
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.80.1.151

Three transcripts from Saccharomyces cerevisiae--CYC1 mRNA (transcribed from the iso-1 cytochrome c gene) and two RNAs of unknown function, designated tr-1 and tr-2--were identified by reverse Southern blot analysis and found to be regulated in response to oxygen. CYC1 mRNA and tr-1 accumulation occurred only in the presence of oxygen while tr-2 appeared only under anaerobic conditions. tr-2 was transcribed from a region approximately 1 kilobase 5′from the CYC1 coding sequence and in the opposite direction. tr-1 showed homology to the same region as tr-2 but was transcribed from elsewhere in the genome. Expression of tr-2 and CYC1 was observed to be normal in cells transformed with centromeric plasmids carrying the two genes. Mutant transforming plasmids were constructed in which a 400-base-pair region between tr-2 and CYC1 was either deleted or inverted. The deletion led to low-level nearly unregulated expression of both the CYC1 and tr-2 genes, suggesting that sequences upstream from both genes are important for their expression and regulation. The inversion mutation produced a reversed pattern of CYC1 regulation in which the mRNA was present in anaerobically grown cells but absent in the presence of oxygen, mimicking wild-type tr-2 regulation and suggesting that the CYC1 transcription unit is under the control of the translocated tr-2 modulator sequences. Models for the function of these modulators are discussed.